Phthalate esters are widely used as plasticisers for polyvinyl chloride. Examples of phthalate esters that are used include dioctyl phthalate, di-isononyl phthalate, di-isodecyl phthalate, di-isooctly phthalate, diisoheptyl phthalate and di-2ethyl hexyl phthalate (DEHP). Typical commercial materials include the Jayflex plasticisers, Jayflex® DINP and Jayflex® DIDP available from ExxonMobil Chemical and the Palatinol® plasticisers marketed by BASF and Vestinol® from Oxeno.
The alcohols from which the plasticiser esters are made are generally obtained by either olefin oligomerisation followed by hydroformylation or by hydroformylation of olefins to form aldehydes followed by aldehyde dimerization, generally by an aldol reaction. The alkyl groups of the esters therefore vary in size and structure according to the process and raw materials used to produce the alcohols. Typical plasticiser esters contain alkyl groups of 5 to 13 carbon atoms, particularly 7 to 13 carbon atoms, and have varying degrees of branching. The size and structure of the alkyl group helps determine the volatility and gellation temperature of the plasticiser and is therefore chosen according to the application in which the plasticised polyvinyl chloride is to be used. For instance flooring, where stain resistance is required, high volatility, at least of the surface layer, is desired.
There is a constant need to improve the properties of plasticisers to provide polyvinyl chloride compositions having improved properties. There is also a need for alternative plasticisers. In addition there is a need to improve the properties of plasticisers. It has also been proposed that esters of cyclohexane carboxylic acids particularly esters of cyclohexane dicarboxylic acids may be used as plasticisers for polyvinyl chloride. For example United States defensive patent publication T 864003 discloses the use of cyclohexane 1-4 dicarboxylate esters as plasticisers. In particular T 864003 discloses bis(2-ethylhexyl)cyclohexane 1-4 dicarboxylate as a plasticiser and compares its performance with bis(2-ethylhexyl)phthalate and finds improved low temperature performance and comparable mechanical properties when using the cyclohexane based material. Such materials are also described in a Union Carbide Chemicals Company Technical Information bulletin Number F-7893B of November 1957 entitled “Flexol” Plasticiser CC-55.
More recently Gebrauchsmuster DE 29824628 and PCT Publication WO 99/32427 disclose a range of plasticisers based on cyclohexane dicarboxylic acid prepared by the hydrogenation of the corresponding phthalates. According to DE 29824628 and WO 99/32427 the cyclohexanoates have lower density and viscosity and yield an improvement in the low temperature flexibility of the plastics when compared with the corresponding phthalates. Properties such as the Shore hardness and other mechanical properties of the resultant plastics are said to be identical to those obtained with the use of phthalates. According to WO 99/32427 the cyclohexanoates exhibit better workability in a dry blend and also have advantages through the markedly lower viscosity when compared with the corresponding phthalates.
Japanese Patent Application Publication Number P 2001 207002 describes cyclohexane dicarboxylic acid esters derived from mixtures containing from 80 to 97 wt % of C9 branched alcohols. Japanese Patent Publication Number P 2001-207002 compares, as plasticisers, these esters with dioctyl phthalate and finds improved cold resistance, viscosity and viscosity stability over time.
We have now found that cyclohexanoates may be used as plasticisers in polyvinyl chloride compositions to reduce the amount of polyvinyl chloride required to produce compositions having comparable mechanical properties to those obtained when using phthalates as the plasticiser.
Accordingly, the present invention provides the use of an ester of cyclohexane polycarboxylic acids as plasticisers for polyvinyl chloride compositions to enable the production of a composition having comparable mechanical properties with a reduced amount of polyvinyl chloride. In some embodiments the amount of polyvinyl chloride can be reduced by 0.05 wt %, 1.5 wt %, 2.0 wt %, 2.5 wt % and 3 wt % or any range thereof resulting in 4 to 7% cost savings at comparably plasticiser price.
In particular, the present invention provides polyvinyl chloride composition based on esters of cyclohexane polycarboxylic acids as plasticisers having Shore hardness and tensile strength comparable to compositions based on phthalate plasticisers but requiring less polyvinyl chloride than when the phthalate plasticiser is used. This results in considerable economic benefits, especially in products prepared from plastisols.
The invention is applicable across the range of plasticised polyvinyl chloride materials. It is applicable to the production of semi-rigid polyvinyl chloride compositions which typically contain from 10 to 40 parts, preferably 15 to 35 parts, more preferably 20 to 30 parts of plasticiser per 100 parts of polyvinyl chloride. The invention is also applicable to flexible polyvinyl chloride compositions which typically contain from 40 to 60 parts preferably 44 to 56 parts, more preferably from 48 to 52 parts per 100 parts of polyvinyl chloride and also to the highly flexible compositions which typically contain from 70 to 110 parts, preferably 80 to 100 parts, more preferably 90 to 100 parts of plasticiser per 100 parts of polyvinyl chloride. The parts being by weight.
The semi-rigid compositions are typically used for the production of pipes, some wire and cable coatings, floor tiles, window shades, films, blood bags and medical tubing. Flexible compositions are typically used for the production of sheeting, upholstery, medical tubing, garden hoses, pool liners, water beds and the like. Very flexible compositions are used in the production of coated cloth, toys, shoe soles and the like. The esters of cyclohexane polycarboxylic acid are particularly useful in the production of medical articles such as blood bags and medical tubing and in toys and materials used for food contact such as bottle caps and films where di-2-ethyhexyl phthalate has traditionally been used and there are some concerns about its toxicity.
In another aspect of the present invention the esters of the cyclohexane polycarboxylic acid are used together with other plasticisers. For example, the ester of the cyclohexane polycarboxylic acid may be used with plasticisers such as adipate esters, phthalate esters, trimellitate esters and various polymeric plasticisers, some of which have been described previously. When used in plasticiser blends the relative proportions of the plasticisers that are used will depend upon the desired properties. However we prefer to use at least 5 wt %, more preferably at least 10 wt %, more preferably at least 15 wt %, more preferably at least 20 wt %, more preferably at least 25 wt %, more preferably at least 30 wt %, more preferably at least 35 wt %, more preferably at least 40 wt %, more preferably at least 45 wt %, more preferably at least 50 wt %, more preferably at least 55 wt %, more preferably at least 60 wt %, more preferably at least 65 wt %, more preferably at least 70 wt %, more preferably at least 75 wt %, more preferably at least 80 wt %, more preferably at least 85 wt %, more preferably at least 90 wt %, of the ester of the cyclohexane polycarboxylic acid based on the total weight of plasticiser present. In a preferred embodiment wherein a mixture of plasticisers is used and one of the plasticisers is a phthalate, the mixture preferably comprises no more than 95 wt % cyclohexane polycarboxylic acid. Preferred ranges include between 0.01 and 95 wt %, more preferably 5 to 90 wt %, more preferably 10 to 80 wt %, more preferably 20 to 70 wt %, more preferably 30 to 60 wt % of the ester of the cyclohexane polycarboxylic acid.
We have also found that cyclohexane polycarboxylic acid esters impart an improved stability to ultra-violet light when used as plasticisers in polyvinyl chloride compositions. This improved stability leads to longer service life for materials made from the polyvinyl chloride especially in an environment where they are subjected to sunlight. Throughout this application ultra-violet light stability is measured in the QUV test which is ASTM G 53-84. This is particularly useful where the plasticised polyvinyl chloride composition is to be used in outdoor applications. In particular, this is useful in applications such as roofing, tarpaulins and tents, films such as adhesive tapes and agricultural films, shoes and automobile interiors.
In a further embodiment the present invention therefore provides a plasticised polyvinyl chloride composition containing from 20 to 100 parts by weight, preferably 30 to 90 parts by weight, more preferably 40 to 80 parts by weight, more preferably 50 to 70 parts by weight of a plasticiser composition containing one or more cyclohexane polycarboxylic acid esters as plasticiser per 100 parts of polyvinyl chloride said composition having a stability to ultra-violet light indicated by the low development of colour in the QUV test over 456 hours in a formulation containing 100 parts of solvic 367 polyvinyl chloride, 50 parts of plasticiser, 5 parts of Durcal calcium carbonate filler and 2 parts of LZB 320 stabiliser.
In a further embodiment the present invention provides the use of a plasticised polyvinyl chloride composition containing from 20 to 100 parts by weight preferably 30 to 90 parts by weight, more preferably 40 to 80 parts by weight, more preferably 50 to 70 parts by weight of a plasticiser composition containing one or more cyclohexane polycarboxylic acid esters as plasticiser per 100 parts by weight of polyvinyl chloride in the production of articles said composition having a stability to ultra-violet light, as indicated by the low development of colour in the QUV test over 456 hours in a formulation containing 100 parts of solvic 367 polyvinyl chloride, 50 parts of plasticiser, 5 parts of Durcal calcium carbonate filler and 2 parts of LZB 320 stabiliser.
In a further embodiment, the invention provides roofing, tarpaulins, tents, films, sheeting, floor covering, shoes and automobile interiors obtained from a plasticised polyvinyl chloride composition containing from 20 to 100 parts by weight preferably 30 to 90 parts by weight, more preferably 40 to 80 parts by weight, more preferably 50 to 70 parts by weight of a plasticiser composition containing one or more cyclohexane polycarboxylic acid esters per 100 parts of polyvinyl chloride.
One widespread use of polyvinyl chloride is as a plastisol. A plastisol is a fluid or a paste consisting of a mixture of polyvinyl chloride and a plasticiser optionally containing various additives. A plastisol is used to produce layers of polyvinyl chloride which are then fused to produce coherent articles of flexible polyvinyl chloride. Plastisols are useful in the production of flooring, tents, tarpaulins, coated fabrics such as automobile upholstery, in car underbody coatings, in mouldings and other consumer products. Plastisols are also used in medical uses such as blood bags and tubing, footwear, fabric coating, toys, flooring products and wallpaper. Plastisols typically contain 40 to 200 parts by weight, more typically 50 to 150 parts by weight, more typically 70 to 120 parts by weight, more typically 90 to 110 parts by weight of plasticiser per 100 parts of polyvinyl chloride.
Plastisols are usually made from polyvinyl chloride that has been produced by emulsion polymerisation or micro suspension polymerisation. The plastisol may be produced by the manufacturer of the polyvinyl chloride or a compounder and shipped to the user in fluid form. Alternatively the plastisol may be produced by the user. In either instance, although particularly when the plastisol is produced by the manufacture of the polyvinyl chloride or a compounder, it is important that the plastisol viscosity be stable over time.
Phthalate esters are widely used as plasticisers in plastisols. However, plastisols based on phthalate ester plasticisers suffer from the disadvantages that the viscosity of the plastisol can be undesirably high and that the viscosity of the plastisol can increase to an undesirable extent over time. We have found that when the cyclohexane polycarboxylic acid esters are used as the plasticiser the plastisols also have improved viscosity stability over time, furthermore they also have improved viscosity. This is particularly useful where the plastisol is to be stored for sometime between production and use, for example when it is used in coating applications.
The present invention therefore provides a plastisol composition containing from 40 to 200 parts by weight preferably 50 to 150 parts by weight, more preferably 70 to 120 parts by weight, more preferably 90 to 110 parts by weight of plasticiser per 100 parts of polyvinyl chloride, wherein the plasticiser comprises one or more cyclohexane polycarboxylic acid esters.
In a further embodiment, the present invention provides a process for the production of flexible polyvinyl chloride comprising forming a layer from a plastisol containing from 40 to 200 parts by weight preferably 50 to 150 parts by weight, more preferably 70 to 120 parts by weight, more preferably 90 to 110 parts by weight of a plasticiser composition containing one or more cyclohexane polycarboxylic acid esters per 100 parts by weight of polyvinyl chloride and subsequently fusing the layer by the application of heat.
The use of the esters of cyclohexane polycarboxylic acids as plasticisers for polyvinyl chloride compositions also provides improved cold flex properties. Cold flex leads to an improved service temperature range and is particularly useful in the production of articles used in a wide range of temperatures. Throughout this application the cold flex properties are measured using the Clash and Berg test (ASTM D 1043-84) and the ASTM D 746 brittleness test. The improved cold flex is particularly useful when the plasticised polyvinyl chloride composition is to be used in articles which are used over a wide temperature range. In particular this is useful in applications such as roofing, tarpaulins and tents, protective films including food wrap films, wire and cable, coated fabrics, shoes and medical applications such as blood bags and tubing.
The present invention therefore provides a plasticised polyvinyl chloride composition containing from 20 to 100 parts by weight preferably 30 to 90 parts by weight, more preferably 40 to 80 parts by weight, more preferably 50 to 70 parts by weight of a plasticiser composition containing one or more cyclohexane polycarboxylic acid esters per 100 parts of polyvinyl chloride having a cold flex below −20° C. as measured by the Clash and Berg test on a formulation of 100 parts of Solvic 271 GC polyvinyl chloride, 150 parts of plasticiser, 80 parts of calcium carbonate filler EXH 1SP from Omya, 6 parts of Tribasic lead stearate and 1 part of dibasic lead searate.
The workability of these plastisols still leaves something to be desired and for applications, such as flexible floor coverings it is usual to include additives which will depress the viscosity of the plastisol to an even lower level than that achieved by using only conventional plasticisers. Lower levels of viscosity are commonly achieved by the inclusion of viscosity depressants which are often hydrocarbon fluids such as dodecyl benzene (DDB) such as Jayflex 602. However these materials are increasingly regarded as unacceptable, particularly in applications such as floor coverings, because the finished articles release noticeable amounts of volatile materials when they are stored or are in use at room temperature.
The problem of increased emissions is exacerbated in applications such as floor coverings which are laminates of several layers of polyvinyl chloride because it is desirable to minimise the amount of plasticiser present in the top coating of the floor covering to improve the wearing properties and stain resistance. For ease of processing it is then necessary to use a high level of viscosity depressant. It would therefore be highly desirable to be able to reduce the viscosity of the plastisol during processing without encountering the problem of increasing the emissions of volatile organic compounds from the finished articles.
Viscosity control is important in the conversion of these plastisols into useful products. For example in the preparation of vinyl floor coverings, the plastisol is spread on a surface moving at around 15 to 25 meters per minute in several layers so that the floor covering is literally built up. Typically these layers include a foam core, a decorative layer and a clear protective wear layer. The multilayer products are first gelled by contact with a heated roll and then passed into an oven where they are fused (gelled) at a temperature of from 180° C. to 200° C. Often the gelling is performed after the spreading of each individual layer, starting with the base or encapsulation layer. After the gelling, the next layer can be spread. When all layers have been spread, the product is then passed into an oven to obtain full fusion of all layers together and adequate expansion of the foamed layers.
To fulfill the plastisol spread coating requirements in terms of production speed (adequate viscosity and adequate gelation) a wide range of viscosity regulators, usually viscosity depressants, are used.
Traditional viscosity depressants used today include hydrocarbon fluids, such as Jayflex 615 or Exxsol D100, dodecyl benzene such as Jayflex 602, sold by ExxonMobil Chemical and 2,2,4-trimethylpentanediol diisobutyrate, sold as Texanol by Eastman Chemical or specialty esters based on oleates and laurates. WO97/35060 discloses a plastisol composition comprising a chlorine-containing resin, a primary plasticiser and a C11-C14 straight chain or branched chain alkyl benzoate.
Although the above products perform well they have limited compatibility (only useful at low concentrations). They also have high volatility, and their effect on gelation temperature, their little or no plasticising effect, their slow fusion with the resin, their cost performance ratio and their contribution to the VOCs emissions from finished products has lead to a search for improved products.
We have now found that the esters of cyclohexane carboxylic acids may be used as viscosity depressants for plastisols particularly plastisols using phthalates as the plasticiser. In a further embodiment the invention therefore provides the use of an ester of a cyclohexane carboxylic acid as a viscosity depressant for plastisols.
In yet a further embodiment the invention provides a plasticised polyvinyl chloride composition comprising polyvinyl chloride and from 20 to 200 preferably 40 to 180, more preferably 60 to 160, more preferably 80 to 140, more preferably 100 to 120 parts per 100 parts of polyvinyl chloride of a plasticiser composition comprising a plasticiser other than an ester of a cyclohexane carboxylic acid ester and an ester of a cyclohexane carboxylic acid wherein the amount of cyclohexane carboxylic acid ester present is greater than 5 wt % of the total plasticiser content.
We have found that levels above 5 wt % of the ester of cyclohexane carboxylic acid provides a significant reduction in viscosity of the plasticiser composition. We prefer to use from, 5 to 50 wt % of the ester of the cyclohexane carboxylic acid, more preferably from 7 to 30 wt %, more preferably from 10 to 20 wt % based on the total weight of plasticiser.
In a preferred system 5 to 20, preferably 7 to 15, more preferably 10 to 15 wt % of total phthalate of the lower viscosity esters of cyclohexanoic polycarboxylic acids particularly diisoheptyl cyclohexane dicarboxylic acid may be used to replace traditional viscosity depressants used in phthalate based formulations such as dodecyl benzene. The use of the ester of cyclohexane polycarboxylic acid will have the added benefit that the ester will also have a plasticising effect.
Where the ester of a cyclohexane mono-carboxylic acid is to be used in conjunction with a primary plasticiser to act as a viscosity depressant the primary plasticisers may be any of those conventionally used for plasticising chlorine containing resins. These include dialkyl esters of phthalic anhydrides and cycloalkane dicarboxylic acids with monohydric alcohols having from 4 to 13 carbon atoms, dibenzoate esters, alkyl esters of aromatic tri- or tetra-carboxylic acids and aliphatic dicarboxylic acid with monohydric alcohols having 3 to 12, preferably 3 to 10, carbon atoms.
Examples of suitable benzenepolycarboxylic acids or a derivatives thereof with which the esters of the cyclohexane carboxylic acids may be used are the alkyl terephthalates such as monomethyl terephthalate, dimethyl terephthalate, diethyl terephthalate, di-n-propyl terephthalate, di-n-butyl terephthalate, di-tert-butyl terephthalate, diisobutyl terephthalate, monoglycol esters of terephthalic acid, diglycol esters of terephthalic acid, di-n-octyl terephthalate, diisooctyl terephthalate, mono-2-ethylhexyl terephthalate, di-2-ethylhexyl terephthalate, di-n-nonyl terephthalate, diisononyl terephthalate, di-n-decyl terephthalate, di-n-undecyl terephthalate, diisodecyl terephthalate, diisododecyl terephthalate, di-n-octadecyl terephthalate, diisooctadecyl terephthalate, di-n-eicosyl terephthalate, monocyclohexyl terephthalate and or dicyclohexyl terephthalate.
Another suitable class are the alkyl phthalates such as monomethyl phthalate, dimethyl phthalate, diethyl phthalate, di-n-propyl phthalate, di-n-butyl phthalate, di-tert-butyl phthalate, diisobutyl phthalate, monoglycol esters of phthalic acid, diglycol esters of phthalic acid, di-n-octyl phthalate, diisooctyl phthalate, di-2-ethylhexyl phthalate, di-n-nonyl phthalate, diisononyl phthalate, di-n-decyl phthalate, diisodecyl phthalate, di-n-undecyl phthalate, diisododecyl phthalate, di-n-octadecyl phthalate, diisooctadecyl phthalate, di-n-eicosyl phthalate, monocyclohexyl phthalate, dicyclohexyl phthalate; alkyl isophthalates such as monomethyl isophthalate, dimethyl isophthalate, diethyl isophthalate, di-n-propyl isophthalate, di-n-butyl isophthalate, di-tert-butyl isophthalate, diisobutyl isophthalate, monoglycol esters of isophthalic acid, diglycol esters of isophthalic acid, di-n-octyl isophthalate, diisooctyl isophthalate, di-2-ethylhexyl isophthalate, di-n-nonyl isophthalate, diisononyl isophthalate, di-n-decyl isophthalate, diisodecyl isophthalate, di-n-undecyl isophthalate, diisododecyl isophthalate, di-n-octadecyl isophthalate, diisooctadecyl isophthalate, di-n-eicosyl isophthalate, monocyclohexyl isophthalate and or dicyclohexyl isophthalate.
Further examples of commercially benzenepolycarboxylic acid esters with which the esters of the cyclohexane carboxylic acids may be used include phthalates such as: Palatinol® AH (Di-(2-ethylhexyl) phthalate; Palatinol® AH L (Di-(2-ethylhexyl) phthalate); Palatinol® C (Dibutyl phthalate); Palatinol® IC (Diisobutyl phthalate); Palatinol® N (Diisononyl phthalate); Palatinol® Z (Diisodecyl phthalate) Palatinol® 10-P (Di-(2-Propylheptyl)phthalate); Palatinol® 711P (Heptylundecyl phthalate); Palatinol™ 911 (Nonylundecyl phthalate); Palatinol® 11P-E (Diundecyl phthalate); Palatinol® M (Dimethyl phthalate); Palatinol® A (Diethyl phthalate); Palatinol® A (R) (Diethyl phthalate); and Palatinol® K (Dibutylglycol phthalate). Further examples are the commercially available adipates such as: Plastomoll® DOA (Di-(2-ethylhexyl)adipate) and Plastomoll® DNA (Diisononyl adipate).
In one embodiment the invention therefore provides a plastisol of low viscosity which can be used to produce finished articles with low emissions of volatile organic compounds. The composition also provides additional unexpected benefits during processing and to the properties of articles fabricated from the composition. The performance of the ester of a cyclohexane mono-carboxylic acid when used in the mixture of resin and primary plasticiser is surprising in the light of conventional wisdom as to the theory pertaining to useful non-exuding plasticisers. The compatibility of plasticisers with PVC (and their non-exuding behaviour) is usually attributed to the presence of diester or triester groups in the plasticisers, or to the combined presence of an ester group and at least one aromatic ring.
We have also found that the use of cyclohexane polycarboxylic acid esters as plasticisers for polyvinyl chloride also results in improved processability of the polyvinyl chloride compositions. This improved processability is particularly useful in the transformation of the plasticised polyvinyl chloride composition. Transformations include, for example, pelletising, extrusion, injection moulding and calendering. Calendering is used in applications such as the production of roofing, protective films including stationery. Extrusion is used in the production of films, pipes, guttering and wire and cable coatings. Injection moulding is used in the production of shoes, toys and the like.
The present invention therefore further provides the use of from 20 to 100 parts preferably from 30 to 90, more preferably from 40 to 80, more preferably from 50 to 70 by weight of a plasticiser composition containing one or more cyclohexane polycarboxylic acid esters per 100 parts of polyvinyl chloride to improve the processability of a polyvinyl chloride formulation.
In a further embodiment the present invention provides a plasticised polyvinyl chloride composition for use in pelletising, extrusion, injection moulding or calendering containing from 20 to 100 parts preferably from 30 to 90, more preferably from 40 to 80, more preferably from 50 to 70 by weight of a plasticiser composition containing one or more cyclohexane polycarboxylic acid esters per 100 parts by weight of polyvinyl chloride.
In a further embodiment the invention provides extruded articles obtained from a plasticised polyvinyl chloride composition containing from 20 to 100, preferably from 30 to 90, more preferably from 40 to 80, more preferably from 50 to 70 parts by weight of a plasticiser composition containing one or more cyclohexane polycarboxylic acid esters per 100 parts of polyvinyl chloride.
In a further embodiment the invention provides pellets comprising polyvinyl chloride and from 10 to 100, preferably from 30 to 90, more preferably from 40 to 80, more preferably from 50 to 70 parts by weight of a plasticiser composition containing one or more cyclohexane polycarboxylic acid esters per 100 parts of polyvinyl chloride.
In a further embodiment the invention provides injection moulded articles obtained from a plasticised polyvinyl chloride composition containing from 20 to 100, preferably from 30 to 90, more preferably from 40 to 80, more preferably from 50 to 70 parts by weight of cyclohexane polycarboxylic acid esters per 100 parts of polyvinyl chloride.
In a further embodiment the invention provides articles obtained by calendering a plasticised polyvinyl chloride composition containing from 20 to 100, preferably from 30 to 90, more preferably from 40 to 80, more preferably from 50 to 70 parts by weight of a plasticiser composition containing one or more cyclohexane polycarboxylic acid esters per 100 parts by weight of polyvinyl chloride.
We have also found that if esters of cyclohexane polycarboxylic acids are used as plasticisers in one of adjacent layers of plasticised polyvinyl chloride and phthalate plasticisers particularly di-2 ethyl hexyl phthalate are used as plasticiser in the other adjacent layer, the migration of the plasticiser from one layer to the other is reduced as compared with adjacent foils, which contain different of differing amounts of phthalate plasticiser. Undesirably high levels of migration can lead to unsightly crinkling of the multi layer foil.
Accordingly, in a further embodiment the present invention provides a multilayer article in which at least two adjacent layers comprise plasticised polyvinyl chloride wherein the plasticiser in one of said two adjacent layers contains an ester of a cyclohexane polycarboxylic acid.
In a further embodiment, the invention provides the use of any one of the cyclohexane polycarboxylic acid esters mentioned herein as a plasticiser for polyvinyl chloride to reduce the migration of plasticiser between adjacent layers of plasticised polyvinyl chloride at least one of which contains a phthalate ester, particularly di-2 ethyl hexyl phthalate as plasticiser.
Another disadvantage of the currently used flexible polyvinyl chloride containing phthalates as plasticisers is occurring during incineration and accidental fires. Due to the high content of the (aromatic) phthalates a heavy smoke generation can be observed during incineration. We have now found that cyclohexane polycarboxylic acid esters impart a reduced tendency to form smoke on burning when used as plasticisers in polyvinyl chloride compositions. This is particularly useful when the plasticised polyvinyl chloride composition is to be incinerated or is accidentally burnt. Accordingly the use of cyclohexanoates instead of the currently used phthalates can provide products with an improved safety aspect during incineration and accidental fires.
As stated previously as well as the more favourable burning properties, use of the cyclohexanoates also provides a better low temperature flexibility and a lower viscosity than the corresponding phthalates. This will enhance the final product properties by providing a broader application temperature range and easier processing if used in plastisol applications.
The use of esters of cyclohexane polycarboxylic acids as plasticisers for polyvinyl chloride can result in an increase in the temperature required for gelation compared to compositions based on comparable phthalates. Accordingly in a further embodiment of the invention fast fusing plasticisers can be added to the composition containing the ester of the cyclohexane polycarboxylic acid.
In plastisol applications where the esters of cyclohexane dicarboxylic acids such as diisononyl cyclohexanoic acid (DINCH) could be using such as wall coverings, flooring, toys, conveyor belts, synthetic leather. Typical formulations could be, in parts by weight
PVC100Fast fusing plasticiser5-25DINCH30-50 Filler0-50Stabilizer1-4 Other0-10
Alternatively typical formulations for use in the production of automotive underbody sealants which typically have high plasticiser and high filler could be in parts by weight
PVC 100 or PVC copolymer 100 (or combinations of the two).Fast fusing plasticiser20-35DINCH60-90Filler such as calcium carbonate 80-150Stabilizer and other additives 0-10
As a further embodiment formulations for the production of calendered floor tiles could be in parts by weight
PVC copolymer 100 or PVC 100 or combinations of the two.Plasticiser fast fusing10-30DINCH20-30Epoxidized soybean oil0-6Filler500-800(CaCO3)pigments, stabilizers, other additives 0-10 or as needed
Similar formulations to those set out above could be used but based on other esters of cyclohexane dicarboxylic acid.
Thick extruded materials would also benefit from the addition of a fast fusing plasticiser. Applications include the thick chair mats, water stops, and extruded profiles. For applications where the extruded material may be thicker than 3-4 mm, if the plasticised PVC is not thoroughly mixed in the extruder, the surface is blemished, sometimes dull, sometimes containing mold marks, waves, or streaks. Adding a little fast fusing plasticiser to the plasticiser blend can correct this problem. Examples of suitable formulations for extrusions in parts per hundred are
PVC100Fast fusing plasticiser5-15DINCH10-30 Filler0-25together with pigments, lubricants, stabilizers, other additives, as needed.
Here again similar formulations based on other esters of cyclohexane dicarboxylic acids could be used.
Examples of non-phthalate fast fusing plasticisers which can be used include diethylene glycol dibenzoate, butyl benzyl phthalate, dipropylene glycol dibenzoate, such as the phenyl cresyl esters of pentadecyl sulfonic aromatic sulfonic acid esters available from Bayer as Mesamoll, citrates such as tributylacetyl citrate, tri-2-ethylhexyl phosphate, trioctyl phosphate such as 2-ethylhexyl-isodecyl phosphate, di-2-ethylhexyl phenyl phosphate, triphenyl phosphate, tricresyl phosphate.
High chlorine content chlorinated paraffins are also known to reduce fusion and fluxing temperatures. Material containing 60 to 70 wt % chlorine can have fusion temps between 75-84° C. while the lower chlorine materials, containing 40 to 54 wt % chlorine, can have fluxing temperatures around 120-135° C.
Low molecular weight diesters such as dibutyl adipate also reduce fusion/flux temperatures although we prefer to use no more than 10 phr of those materials because larger amounts could create an undesirable rise in volatility.
In the embodiments of the present invention reference to systems containing the esters of the cyclohexane carboxylic acids are to systems in which the ester of the cyclohexane carboxylic acid is the sole plasticiser and also to systems in which it is present in admixture with other plasticisers.
Polyvinyl chloride is available in many different forms—the variations being in the molecular weight of the polymer, the molecular weight distribution of the polymer, the particle size of the polymer particles, the particle size distribution and the surface aspect of the particles which may be coarse or smooth. Another variable in polyvinyl chloride is the degree of chain branching. The vinyl polymer may be a copolymer (e.g. a copolymer of vinyl chloride and vinyl acetate). Polymers of vinyl chloride may be obtained by suspension polymerisation or emulsion polymerisation. In suspension polymerisation, vinyl chloride monomer is suspended in water with agitation under carefully controlled temperature and pressure. The batch will also contain suspending agents and initiators. After polymerisation is complete, the batch is discharged to a stripper where unreacted monomer is removed. Finally, the suspension is washed and dried to obtain the suspension polyvinyl chloride.
Typical suspension polymerised polyvinyl chloride consists of agglomerated particles of size in the range 80 to 200 microns. Polyvinyl chloride produced by suspension polymerisation is typically used in dry blend applications. Emulsion polymerised polyvinyl chloride is produced in a similar manner to suspension polyvinyl chloride except that the vinyl chloride monomer is emulsified in water so that the polymerisation results in latex particles. The ratio of water to vinyl chloride monomer in emulsion polymerisation is greater than the ratio of water to vinyl chloride monomer in suspension polymerisation. Emulsion polymerised polyvinyl chloride also consists of agglomerated particles but the particles are generally smaller than the particles of suspension polymerised polyvinyl chloride. Typically, the agglomerated particles of emulsion polyvinyl chloride have a particle size in the range of 15 to 20 microns. Emulsion polymerised polyvinyl chloride is generally used in the production of plastisols which are used in coating operations where the plastisol is coated onto a substrate and is then fused by heating.
Polyvinyl chloride of particle size between 1 and 40 microns may be produced by micro suspension polymerisation.
Different forms of polyvinyl chloride are used in different applications. One important property is the mean molecular weight of the polymer. A factor known as the K value is used to indicate the mean molecular weight of polyvinyl chloride. The K value is the viscosity of a 0.005 wt % solution of the polyvinyl chloride in cyclohexanone at 25° C. as measured using an Ubbelhode viscometer. The K value is the German standard DIN 53726. The K value of the polyvinyl chloride impacts the fusion temperature and gellation rate of the plasticised polyvinyl chloride composition. The K value also influences the melt viscosity of the plasticised polyvinyl chloride composition and the rate at which the composition can be foamed. Typically the higher the K value the better the mechanical properties but the lower the flowability. Accordingly, the formulator of polyvinyl chloride will select the nature of the polyvinyl chloride and the nature of the plasticiser to optimise the properties for a particular use.
Where plasticised polyvinyl chloride is to be used in calendering operations, it is preferred to use a suspension polymerised polyvinyl chloride having a K value in the range 65 to 70. Where the plasticised polyvinyl chloride is to be used in wire and cable applications, it is preferred to use a suspension polymerised polyvinyl chloride having a K value above 70. For injection moulding, a polyvinyl chloride having a K value of 60 to 67 is preferred. Emulsion polymerised polyvinyl chloride is preferred for applications where good flow of the plasticised polyvinyl chloride is required such as spread coating, as used in the manufacture of flooring, chemical foaming, dip coating and rotational moulding. For spread coating an emulsion polyvinyl chloride of K value 65 to 75 is preferred and for chemical foaming, dip-coating and rotational moulding a K value of 65 to 70 is preferred.
The plasticisers used in the present invention are esters of cyclohexane polycarboxylic acids. The cyclohexane polycarboxylic acids may be the 1,2 dicarboxylic acids, the 1,3 dicarboxylic acids or the 1,4 dicarboxylic acids. Alternatively, the plasticisers may be esters of the tricarboxylic acids such as 1,3,5, 1,2,3 and 1,2,4 tricarboxylic acids. Mixtures of these acids may also be used. Any alcohol may be used to esterify the acids although it is preferred to use alcohols containing from 5 to 20 carbon atoms in particular alcohols containing from 8 to 12 carbon atoms are preferred.
The Hexamoll DINCH product recently introduced by BASF is an example of a cyclohexane dicarboxylic acid ester which can be used in the present invention. U.S. Pat. No. 6,284,917 to BASF provides an illustration of one method by which these materials may be prepared.
Examples of cyclohexane carboxylic acid esters which may be used in the various embodiments of the present invention include 1,2-cyclohexane dicarboxylic acid diisobutyl, 1,2-cyclohexane dicarboxylic acid dicyclohexyl, 1,2-cyclohexane dicarboxylic acid diiso heptyl, 1,2-cyclohexane dicarboxylic acid di (3,5,5-trimethyl hexyl), 1,2-cyclohexane dicarboxylic acid di (2,6-di methyl-4-heptyl), 1,2-cyclohexane dicarboxylic acid diisodecyl, 1,2-cyclohexane dicarboxylic acid diisoundecyl, 1,2-cyclohexane dicarboxylic acid diiso tridecyl, 1,2-cyclohexane dicarboxylic acid diiso octadecyl, diiso octadecyl, 3-methyl-1,2-cyclohexane dicarboxylic acid diisobutyl, 3-methyl-1,2-cyclohexane dicarboxylic acid dicyclohexyl, 3-methyl-1,2-cyclohexane dicarboxylic acid diiso heptyl, 3-methyl-1,2-cyclohexane dicarboxylic acid di (2-ethylhexyl), 3-methyl-1,2-cyclohexane dicarboxylic acid di (3,5,5-trimethyl hexyl), 3-methyl-1,2-cyclohexane dicarboxylic acid di (2,6-di methyl-4-heptyl), 3-methyl-1,2-cyclohexane dicarboxylic acid diisodecyl, 3-methyl-1,2-cyclohexane dicarboxylic acid diisoundecyl, 3-methyl-1,2-cyclohexane dicarboxylic acid diiso tridecyl, 3-methyl-1,2-cyclohexane dicarboxylic acid diiso octadecyl, 4-methyl-1,2-cyclohexane dicarboxylic acid diisobutyl, 4-methyl-1,2-cyclohexane dicarboxylic acid dicyclohexyl, 4-methyl-1,2-cyclohexane dicarboxylic acid diiso heptyl, 4-methyl-1,2-cyclohexane dicarboxylic acid di (3,5,5-trimethyl hexyl), 4-methyl-1,2-cyclohexane dicarboxylic acid di (2,6-di methyl-4-heptyl), 4-methyl-1,2-cyclohexane dicarboxylic acid diisodecyl, 4-methyl-1,2-cyclohexane dicarboxylic acid diisoundecyl, 4-methyl-1,2-cyclohexane dicarboxylic acid diiso tridecyl, 4-methyl-1,2-cyclohexane dicarboxylic acid diiso octadecyl.
Cyclohexane polycarboxylic acid straight chain alkyl ester, usually, jointly using with one, two or more kinds of the aforementioned alicyclic polycarboxylic acid branched alkyl ester and/or cycloalkyl ester may also be used.
Examples of the straight chain alkyl ester include 1,2-cyclohexane dicarboxylic acid di heptyl, 1,2-cyclohexane dicarboxylic acid dioctyl, 1,2-cyclohexane dicarboxylic acid di decyl, 1,2-cyclohexane dicarboxylic acid di undecyl, 1,2-cyclohexane dicarboxylic acid di dodecyl, 1,2-cyclohexane dicarboxylic acid di tetradecyl, 1,2-cyclohexane dicarboxylic acid dihexadecyl, 1,2-cyclohexane dicarboxylic acid dioctadecyl, 3-methyl-1,2-cyclohexane dicarboxylic acid di heptyl, 3-methyl-1,2-cyclohexane dicarboxylic acid dioctyl, 3-methyl-1,2-cyclohexane dicarboxylic acid di decyl, 3-methyl-1,2-cyclohexane dicarboxylic acid di undecyl, 3-methyl-1,2-cyclohexane dicarboxylic acid di dodecyl, 3-methyl-1,2-cyclohexane dicarboxylic acid di tetradecyl, 3-methyl-1,2-cyclohexane dicarboxylic acid dihexadecyl, 3-methyl-1,2-cyclohexane dicarboxylic acid dioctadecyl, 4-methyl-1,2-cyclohexane dicarboxylic acid di heptyl, 4-methyl-1,2-cyclohexane dicarboxylic acid dioctyl, 4-methyl-1,2-cyclohexane dicarboxylic acid di decyl, 4-methyl-1,2-cyclohexane dicarboxylic acid di undecyl, 4-methyl-1,2-cyclohexane dicarboxylic acid di dodecyl, 4-methyl-1,2-cyclohexane dicarboxylic acid di tetradecyl, 4-methyl-1,2-cyclohexane dicarboxylic acid dihexadecyl, 4-methyl-1,2-cyclohexane dicarboxylic acid dioctadecyl.
Other cyclohexane carboxylic acid esters include those derived from phthalates and in particular the following: cyclohexane-1,2-dicarboxylic acid di(isopentyl) ester, obtainable by hydrogenation of a di(isopentyl)phthalate having the Chemical Abstracts registry number (in the following: CAS No.) 84777-06-0; cyclohexane-1,2-dicarboxylic acid di(isoheptyl) ester, obtainable by hydrogenating the di(isoheptyl)phthalate having the CAS No. 71888-89-6; cyclohexane-1,2-dicarboxylic acid di(isononyl) ester, obtainable by hydrogenating the di(isononyl)phthalate having the CAS No. 68515-48-0; cyclohexane-1,2-dicarboxylic acid di(isononyl) ester, obtainable by hydrogenating the di(isononyl)phthalate having the CAS No. 28553-12-0, which is based on n-butene; cyclohexane-1,2-dicarboxylic acid di(isononyl) ester, obtainable by hydrogenating the di(isononyl)phthalate having the CAS No. 28553-12-0, which is based on isobutene; a 1,2-di-C9-ester of cyclohexane dicarboxylic acid, obtainable by hydrogenating the di(nonyl)phthalate having the CAS No. 68515-46-8; cyclohexane-1,2-dicarboxylic acid di(isodecyl) ester, obtainable by hydrogenating a di(isodecyl)phthalate having the CAS No. 68515-49-1; 1,2-C7-11-ester of cyclohexane dicarboxylic acid, obtainable by hydrogenating the corresponding phthalic acid ester having the CAS No. 68515-42-4; 1,2-di-C7-11-ester of cyclohexane dicarboxylic acid, obtainable by hydrogenating the di-C7-11-phthalates having the following CAS Nos.: 111381-89-6, 111381-90-9, 111381-91-0, 68515-44-6, 68515-45-7 and 3648-20-7; a 1,2-di-C9-11-ester of cyclohexane dicarboxylic acid, obtainable by hydrogenating a di-C9-11-phthalate having the CAS No. 98515-43-5; a 1,2-di(isodecyl)cyclohexane dicarboxylic acid ester, obtainable by hydrogenating a di(isodecyl)phthalate, consisting essentially of di-(2-propylheptyl)phthalate; 1,2-di-C7-9-cyclohexane dicarboxylic acid ester, obtainable by hydrogenating the corresponding phthalic acid ester, which comprises branched and linear C7-9-alkylester groups; respective phthalic acid esters which may be e.g. used as starting materials have the following CAS Nos.: di-C7-9-alkylphthalate having the CAS No. 111 381-89-6; di-C7-alkylphthalate having the CAS No. 68515-44-6; and di-C9-alkylphthalate having the CAS No. 68515-45-7.
More preferably, the above explicitly mentioned C5-7, C9, C10, C7-11, C9-11 and C7-9 esters of 1,2-cyclohexane dicarboxylic acids are the hydrogenation products of the commercially available benzenepolycarboxylic acid esters with the trade names Jayflex® DINP (CAS No. 68515-48-0), Jayflex® DIDP (CAS No. 68515-49-1), Palatinol® 9-P, Vestinol® 9 (CAS No. 28553-12-0), TOTM-I® (CAS No. 3319-31-1), Linplast® 68-TM and Palatinol® N (CAS No. 28553-12-0) which are used as plasticisers in plastics.
A particularly preferred ester comprises a mixture of diesters of cyclohexanoic dicarboxylic acid with a mixture of alcohols having an average carbon number between 8.5 and 9.5 in whose 1H-NMR spectrum, obtained in deuterated choroform (CDCl3), the ratio [R2] of the surface area below the resonance signals with chemical shifts in the range between the lowest valley close to 1.0 and 2.0 towards tetramethylsilane (TMS) to the surface area below the resonance signals with chemical shifts in the range between 0.5 and the lowest valley close to 1.0 ppm towards TMS is between 1.35 and 5.50.
In the 1H-NMR-measurement used to characterise the alcohols used to produce the esters a dilute solution of the alcohol in deuteroform is used as the sample and the average carbon number is determined as follows. The alkyl-protons between 2 and 0.4 ppm are integrated and the —CH2O-protons between 3.9 and 3 ppm are also integrated. The hydroxyl proton can be observed between 3 and 2 ppm. With I (n−m ppm) representing the integration of the region between n and m ppm relative to TMS:
      Average    ⁢                  ⁢    carbon    ⁢                  ⁢    number    =            (                        I          ⁡                      (                          2              -                              0.4                ⁢                                                                  ⁢                ppm                                      )                          +                  0.5          ×                      I            ⁡                          (                              3.9                -                                  3                  ⁢                                                                          ⁢                  ppm                                            )                                          )              I      ⁡              (                  3.9          -                      3            ⁢                                                  ⁢            ppm                          )            
For the phthalates, the —CH2O-protons of the ester group are seen in the region between 6 and 3 ppm, typically between 5 and 3.5 ppm. The protons on the aromatic ring are seen before 7.5 ppm and do not influence the integration. The above formula for the phthalates is therefore as follows:
      Average    ⁢                  ⁢    carbon    ⁢                  ⁢    number    =                    (                              I            ⁡                          (                              2                -                                  0.4                  ⁢                                                                          ⁢                  ppm                                            )                                +                      0.5            ×                          I              ⁡                              (                                  5                  -                                      3.5                    ⁢                                                                                  ⁢                    ppm                                                  )                                                    )            /              I      ⁡              (                  5          -                      3.5            ⁢                                                  ⁢            ppm                          )            
The formulae used are based on the stoichiometric formula of a saturated primary alcohol. If it has an average carbon number of x, its formula isH—O—CH2—(C(x−1)H(2n−1))
The arithmetic takes the (2n−1) from the alkyl chain excluding the —CH2O-protons, adds 0.5×2=1 from the —CH2O— protons. This sums up to 2n in the numerator. The denominator is the 2 from the —CH2O-protons, and 2n/2 makes n, i.e. the average carbon number on the alkyl chain.
For cyclohexanoates, one has to discount the 8 protons on the cyclohexane ring in each molecule, and which are showing up also in the range 1.0-2.0 ppm, amongst the protons of the alkyl chain. This can be done by substracting from the numerator 2 times the I (5−3.5 ppm), as there are 8 such protons in the ring against 4 —CH2O-protons in each cyclohexanoate molecule. Hence for cyclohexanoates
      Average    ⁢                  ⁢    carbon    ⁢                  ⁢    number    =                    (                              I            ⁡                          (                              2                -                                  0.4                  ⁢                                                                          ⁢                  ppm                                            )                                -                      1.5            ×                          I              ⁡                              (                                  5                  -                                      3.5                    ⁢                                                                                  ⁢                    ppm                                                  )                                                    )            /              I      ⁡              (                  5          -                      3.5            ⁢                                                  ⁢            ppm                          )            
In certain embodiments of the invention the cycloalkane plasticisers described herein preferably exclude a 1,2-cyclohexane dicarboxylic acid diester obtained by esterifying 1,2-cyclohexane dicarboxylic acid and mixed aliphatic monohydric alcohols of from 4 to 13 carbons, characterised in that the above mentioned mixed aliphatic monohydric alcohols comprise from 80 to 97% by weight of C9 branched alcohols and from 3 to 20% by weight of alcohols other than C9 branched alcohols.
The esters may be obtained by the esterification of the cyclohexane polycarboxylic acids or the corresponding anhydrides. Alternatively they may be prepared by the Diels Alder condensation of butadiene and maleic anhydride followed by hydrogenation and esterification. Another method by which the esters may be obtained is the hydrogenation of the corresponding phthalates as is described in PCT Publication WO 99/32427.
The polyvinyl chloride and the ester of the cyclohexane polycarboxylic acid may be mixed by the conventional formulating techniques currently used in the production of plasticised polyvinyl chloride formulations. The formulator will attempt to provide a versatile composition having a good balance of properties at reasonable cost. The formulator will be concerned to optimise the balance between end-product properties such as flexibility, low temperature performance, flame resistance, high temperature resistance, volatility, stain resistance, electrical properties and processability and the processing properties such as plastisol viscosity, fusion, dry blending, emissions and printability.
The formulations containing the polyvinyl chloride and the plasticiser may contain other additives. The majority of formulations will contain a stabiliser which counters the effects of ageing; heat stabilisers also reduce the dehydrodehalogenation of the polyvinyl chloride at the temperatures at which the formulation is processed. Stabilisers, such as benzotriazole and benzophenone, also reduce the degradation by sunlight, ozone and biological agents. The improved ultra-violet stability obtained by the use of the esters of the cyclohexane polycarboxylic acids according to the present invention may enable smaller amounts of stabilisers to be used. Typically, the formulations contain from 0.5 to 10 parts, normally from 1.5 to 3 parts, by weight of stabiliser per 100 parts of the polyvinyl chloride.
Stabilizers to provide stability during heat processing are typically metal compounds, particularly lead salts, which are used in wire and cable applications, organotin compounds, barium, cadmin and zinc salts or calcium/zinc stabilisers. Organic phosphates and polyols may also be used. Lead stabilisers are used in wire and cable applications. Calcium/zinc stabiliser systems are used in wire and cable, foil and sheeting, wall coverings, medical applications, tubes and footwear, food packaging film and fabric coating. Barium/zinc stabiliser systems are used in foil and sheeting, flooring, wall covering, tubes and footwear and fabric coating. Tin stabilisers are used in flooring and wall covering. Zinc compounds are frequently used as a stabiliser and as a kicker in formulations used to produce foams in, for example, flooring, wall covering and fabric coating.
Other ingredients which may be added to the polyvinyl chloride formulations include fillers such as calcium carbonate, titanium dioxide or silica. When used, the filler may be present in an amount up to 150 parts, preferably up to 100 parts per 100 parts of polyvinyl chloride. Lubricants, pigments and processing acids may be included. Other ingredients will be chosen according to the use to which the formulation is to be put. For example, the formulation may contain flame retardants, blowing agents and kickers, bio-stabilisers, antistatic agents, viscosity regulators such as thickeners and thinners, antifogging agents which are particular useful is packaging films and antioxidants, such as bisphenol A.
Fillers are incorporated in the formulations to reduce cost, increase the output of dry blending, increase electrical resistance, increase resistance to ultra-violet light, increase hardness, produce improved heat transmission, increase the resistance to heat deformation. Fillers can also impart anti-blocking or anti-slip performance. Examples of suitable fillers include calcium carbonate, clays such as alumino-silicates, silica, dolomite and bauxite.
The particular particle size distribution and average surface area of the filler will be chosen according to the properties it is desired to impart.
Lubricants and processing aids may be included to reduce the adhesion between polyvinyl chloride and hot machinery surfaces during processing. The lubricants also affect the frictional properties between resin particles during processing. Examples of lubricants include stearic acid and metal stearates which can also act as stabilisers. Other lubricants that may be used include petroleum waxes, silicon oil, mineral oil, synthetic oils and polyethylene waxes.
The formulations may also contain flame retardants to increase ignition time, reduce flame spreading and rate of burning. The flame retardants should have a high decomposition temperature, low volatility, a minimum effect on thermal and mechanical properties and good resistance to light and ultra-violet radiation. Examples of flame retardants that may be used include halogen containing compounds and phosphorous containing organic compounds such as triaryl, trialkyl or alkyl diaryl phosphate esters. Other materials that may be used include chloroparaffins, aluminum trihydrate Al(OH)3 or antimony oxides Sb2O3.
Where the formulations are used to produce foams such as in flooring materials, they can contain a blowing agent which decomposes with the evolution of gas bubbles during processing of the plastisol. Examples of suitable blowing agents include azodicarbonamide which releases nitrogen when heated to a temperature in the range 200° C. to 250° C. The system may also contain kickers which control and lower the decomposition temperature of the blowing agent. For example lead compounds such as dibasic lead phthalate, zinc oxide or barium/cadmium compounds may be used to reduce the activation temperature of azodicarbonamide to a temperature in the range 150° C. to 215° C. These metal compounds can also act as stabilisers.
The present invention is illustrated by the following examples in which the C7, C8, C9 and C10 esters of bis-1,2-cyclohexanedicarboxylic anhydride were prepared using the commercial C7 alcohol available from ExxonMobil Chemical Exxal 7 to produce the C7 ester (DIHCH), 2 ethyl hexanol to produce the C8 ester (DEHCH), the commercial C8 alcohol available as Exxal 8 from ExxonMobil Chemical to produce C8 ester (DIOCH), the commercial C9 alcohol available from ExxonMobil Chemical as Exxal 9 to produce the C9 ester (DINCH) and the commercial C10 alcohol available from ExxonMobil Chemical as Exxal 10 to produce the C10 ester (DIDCH). A standard esterification procedure using a titanium catalyst was used such as is described in the Encyclopedia of Chemical Technology, Jaqueleine I Kroschwitz, Mary Howe-Grant, fourth edition, vol 9 pages 755-780 by John Wiley and Sons. For ease of reference the materials are referred to as cyclohexanoic esters.
The reaction therefore proceeds as follows.

The properties of the materials were measured using the test methods set out in Table 1 and were found to be as shown in Table 1:
TABLE 1PropertyMethodUnitDIHCHDEHCHDINCHDIDCHViscosity @ASTMmPa*s34.045.564.787.020° C.D445Density @ASTMg/cm30.9610.9550.9460.94320° C.D4052Water contentASTMppm1546411169E1064Acid valueASTMmg/g0.110.030.030.04D1045KOH
The properties of the cyclohexanoic esters were compared to those of the corresponding phthalates made with the same alcohols, di-2-ethyl hexyl phthalate (DEHP); di-isoheptyl phthalate (Jayflex 77); di-isononyl phthalate (DINP) and di-isodecyl phthalate (DIDP).
FIG. 1 plots the viscosity and density of the different esters against the carbon number of the alcohol used to make the ester. FIG. 1 shows that the viscosity of the cyclohexanoic ester is below that of the corresponding phthalate. This will lead to a lower viscosity of plastisols based on the cyclohexanoic esters and therefore to easier processing of the plastisols.
FIG. 1 also shows that the density of the cyclohexanoic ester is below the density of the corresponding phthalate. This has the benefit that in formulations using the cyclohexanoic ester as plasticiser the volume of the same weight of the plasticised polyvinyl chloride is greater than in comparable formulations using the phthalate ester as the plasticiser. This enables more final product to be made from formulations containing less polyvinyl chloride, in addition the lower efficiency of the cyclohexanoate esters reinforces this effect.